BBC News reports Google is fixing an Android issue that allows hackers to steal calendar and contact application data. The fix is expected to be rolled out over the next few days.
It follows a warning from German security researchers that more than 99% of handsets were potentially leaking information.
The flaw meant hackers could have gained access to data within the phones' calendar and contacts applications.
Such issues are likely to become more frequent, warned security experts.
Google said in a statement: "We're starting to roll out a fix which addresses a potential security flaw that could, under certain circumstances, allow a third party access to data available in calendar and contacts.